1. Field of the Invention
The present invention relates to a controller and a method for detecting a vehicle abnormality.
2. Description of Related Art
Various methods for detecting an abnormality of a vehicle speed sensor have been proposed. For example, JP-A-Hei 10-18896 discloses a method for detecting an abnormality of a vehicle speed sensor based on a throttle opening and a vehicle speed detected by the vehicle speed sensor.
The method of JP-A-Hei 10-18896 for detecting an abnormality of a vehicle speed sensor is depicted in FIG. 8. and includes a first step S101 of checking whether an engine speed sensor and a throttle opening sensor are normal. If the throttle opening sensor and the like are determined as normal, the method goes to step S102 to determine whether a shift lever is positioned at a drive range, and whether the throttle opening is equal to or greater than a predetermined opening. If the shift lever is positioned at the drive range and the throttle opening is equal to or greater than the predetermined opening, the method goes to step S103 to determine whether the vehicle speed sensor detects a vehicle speed of 0 km/h. If the vehicle speed sensor detects a vehicle speed of 0 km/h, the method goes to step S104 to determine whether the engine speed decreases at a given rate. If the engine speed decreases at a given rate, the method goes to step S105 to determine whether the throttle opening is constant. If the throttle opening is constant, there is determined to be a failure in the vehicle speed sensor and in the wiring connected to the vehicle speed sensor.
According to JP-A-Hei 10-18896, the aforementioned method accurately determines whether there is a failure in the vehicle detection system.
An electronic continuously variable transmission (ECVT) is also known. Generally, in an ECVT-mounted vehicle, a change-gear ratio is controlled based on the vehicle speed and throttle opening. Thus, when an abnormality occurs in the vehicle speed detection system, an improper change-gear ratio may be selected. This may cause difficulty in driving. Therefore, the need for early detection of an abnormality in the vehicle speed detection system of an ECVT-mounted vehicle is intensified.
However, as shown in FIG. 8, unless the throttle opening is equal to or greater than a predetermined opening, no abnormality is detected in the vehicle speed detection system by the method of JP-A-Hei 10-18896. Thus, an abnormality in the vehicle speed detection system is not detected early enough.